title: Propagation and stability characteristics of a 500-m-long laser-based fiducial line for high-precision alignment of long-distance linear accelerators.
abstract: A laser-based alignment system with a He-Ne laser has been newly developed in order to precisely align accelerator units at the KEKB injector linac. The laser beam was first implemented as a 500-m-long fiducial straight line for alignment measurements. We experimentally investigated the propagation and stability characteristics of the laser beam passing through laser pipes in vacuum. The pointing stability at the last fiducial point was successfully obtained with the transverse displacements of ±40 μm level in one standard deviation by applying a feedback control. This pointing stability corresponds to an angle of ±0.08 μrad. This report contains a detailed description of the experimental investigation for the propagation and stability characteristics of the laser beam in the laser-based alignment system for long-distance linear accelerators.
authors.affiliation: Accelerator Laboratory, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Suwada
authors.forename: Masanori
authors.initials: M
authors.lastname: Satoh
authors.forename: Souichi
authors.initials: S
authors.lastname: Telada
authors.forename: Kaoru
authors.initials: K
authors.lastname: Minoshima